Long-chain alkenyl succinic acids, esters, and anhydrides as fuel detergents



United States Patent 3,346,354 LONG-CHAIN ALKENYL SUCCI'NIC ACIDS,ESTERS, AND ANHYDRIDES AS FUEL DETERGENTS George J. Kautsky, El Cerrito,and Eddie G. Lindstrom,

Martinez, Calif., assignors to Chevron Research Company, a corporationof Delaware No Drawing. Filed July 2, 1963, Ser. No. 292,450

3 Claims. (CI. 44-63) ABSTRACT OF THE DISCLOSURE This invention isconcerned with fuel compositions having incorporated therein metal freedetergent additives. More particularly it is concerned with fuelcompositions containing as deposit-suppressing detergent additives,alkenyl succinic acids, anhydrides and esters.

In recent years spark-ignition internal combustion engines have beendesigned and built by the industry with the emphasis being placed uponhigher ratios, larger engines and high volumetric efiiciency at highspeeds. Volumetric efiiciency is dependent upon such factors asunhindered flow of fuel-air mixtures through valves and ports, and themaintenance of high compression by eflicient valve closure and timing.However, most fuels in use today when employed in such engines undergodeterioration and leave hard carbonaceous deposits on intake valveunderheads and stems and in the valve ports, interfering with propervalve seating and causing a consequent loss of power and thus requiringfrequent maintenance in order that engines may develop their maximumefficiency as to power and fuel consumption. These deposits result inpart from puff-back of decomposition products from the compressionchamber and in part from decomposition of crankcase oil entering by wayof the valve stem. The deposits may also contain lead compounds thatresult from the decomposition of leadcontaining octane improvers. Thesedeposits attach firmly to the valves and ports and the fuel detergentsthat are in current use in fuels have little or no effect in eitherreducing the deposits already formed or preventing the formation of newharmful deposits.

In addition to the problems caused in spark-ignition engines, fueldeposits cause serious operational problems in compression ignition ordiesel type engines. An especially serious problem is the deposition oflacquer and other carbonaceous materials within the fuel injector tipsof such engines. These cause injector sticking, interfere with injectorseating and alter the fuel spray patterns and thus ultimately affect thecombustion of the fuel, reducing power and seriously affecting theeconomy of engine operation.

In the operation of turbine and jet type engines, fuel deposits whichresult from the high temperatures to which the fuels are subjected,cause serious problems resulting in the plugging of filters and causingpoor heat exchange.

3,346,354 Patented Oct. 10, 1967 Therefore, there exists a serious needfor additives which, when added in proper amounts to fuel compositions,will reduce deposit formation and even reduce deposits that are alreadypresent due to prior operation with fuels which have formed heavydeposits.

It has now been found that superior liquid hydrocarbon fuelcompositions, resistant to harmful deposit formation result from theaddition to the compositions of minor amounts of alkenyl succinic acids,the corresponding alkenyl succinic anhydrides, and the lower mono anddialkyl esters of said acids, wherein the alkenyl groups contain from 50to 250 carbon atoms and the alkoxy groups of the esters contain from 1to 6 carbon atoms.

Thus, the alkenyl succinic anhydrides mentioned above can be prepared byreacting maleic anhydride with a suitable polyolefin, preferably apolyolefin derived from olefins containing from 2 to 5 carbon atoms.Examples are ethylene, propylene, l-butene, 2-butene, isobutene andmixtures of said olefins. A preferred polyolefin is a polyisobutenehaving a molecular weight from about 400 to 3500 and more preferablyfrom 800 to 3200.

The preferred compound is the (ii-tertiary butyl ester of a substitutedsuccinic acid which is produced from polyisobutene having a molecularweight of about 3000.

In addition to the deposit suppressing and detergent qualities of theaforementioned compounds, they possess an additional desiredcharacteristic in that they display good non-emulsifying properties infuel compositions. A common defect of many surface-active additives isthe property of forming undesirable emulsions of water with thehydrocarbon stocks in which they are employed. The emulsion formation iseffectively suppressed by use of compounds such as the tertiary-alkylesters and the polyisobutenyl succinic anhydrides of this invention,which represent especially desirable classes of compounds, impartingexcellent detergency characteristics, and no emulsifying properties tothe compositions.

The effective amount of the additive that must be added to impart thedesired anti-deposit characteristics will vary according to the natureand use of each particular base fuel, however, in general, amounts from50 p.p.m. to 1000 p.p.m. are suflicient, and under most circumstances anamount from 50 to 500 p.p.m. is preferred.

The addition to the fuel compositions of a minor proportion of a lightpetroleum oil in addition to the abovedescribed compounds furtherenhances the deposit-suppressing effect and makes it possible to reducethe amount of succinic acid derivative in the compositions and achieve alike desirable reduction of deposit formation. The light petroleum oilmay be any low viscosity petroleum oil fraction, preferred examplesbeing neutral oils in the range of from 50 to 480 SSU at F. A specificexample is an oil having a viscosity of 60 SSU at 100 F. The use ofthese oils in minor proportions from 5,000 to 15,000 p.p.m. iseffective, a preferred amount being in the range of from 5,000 to 10,000p.p.m.

The succinic acid derivatives of this invention may be prepared byreactions well known in the art. The polymerization of olefins isespecially well-known and the method employed has no effect upon thecompounds described herein and thus any available process may be usedfor this step.

The aforementioned reaction of tit-polyolefin and maleic anhydride toproduce an alkenyl succinic anhydride can 3 be described by thefollowing formulae, using polyisobutene as an example:

in which n is an integer from about 10 to about 60.

The production of alkenyl succinic acids from their correspondinganhydrides may be effected by any known method of hydrolysis, i.e.,heating with water, acid hydrolysis, etc.

Thus the reaction can be carried out using molar ratios of polyolefin toanhydride of from 1:1 to 1:10 and preferably from 1:1 to 1:5. Thereaction temperature may vary from 300 to 500 F., a range of from about425 to 475 F. is preferred because of the high yields obtained.

The esterification reaction used to produce the ester derivatives ofthis invention may be carried out by any commonly used method. Forexample, acid catalyzed esterification with alcohols or oxides, orreaction with olefins in the presence of acid catalysts, such assulfuric acid.

The aforementioned alkenyl succinic esters may be produced by reactionof the acids with alcohols or the anhydrides with alkylene oxides. 4

Reaction of the anhydrides with alcohols results in the formation of amono ester or acid ester in which one carhoxyl radical is notesterified. Both the mono and diesters show good detergent effect andthe above-mentioned methods of esterification are highly desirablemethods, with high yields, yields of from 80% to near 100% being common.The production of the mono esters by reaction of anhydrides with alkyloxides is essentially quantitative.

The following examples illustrate the preparation of the additives ofthis invention. The examples are intended to be only illustrative andnot limiting. Amounts are on a weight basis unless otherwise specified.

Example I.Preparation of polyis'obutenyl succinic anhydride 1 mole ofpolyisobutene, having an average molecular weight of 1000, was placed ina 3-neck 2-liter flask equipped with a thermometer, mechanical stirrerand reflux condenser. The material was heated to 240 C. at which pointmolten maleic anhydride was added dropwise at such a rate that atemperature of 240 C. was maintained without further heating. Two molesof maleic anhydride were added over the course of 6 hours. The excessmaleic anhydride was then stripped from the reaction mixture undervacuum. The reaction product was diluted with 150 neutral oil andfiltered through diatomaceous earth to remove a small amount ofby-products. The yield of anhydride was 860 g. or 80% of theoreticalbased upon polyisobutene.

Example II.Preparatin of polyisobutenyl succinic acid 1 mole ofpolyisobutenyl succinic anhydride, prepared by the process described inExample I, was heated with 2 moles of water for a period of 6 hours at100 C. The mixture was allowed to cool and the water layer wasdiscarded. The yield of acid was 95% based upon the weight of anhydride.

Example Il1.-Preparation of di-tertiarybutyl ester of polyisobutenylsuccinic acid An amount of a 30% solution of polyisobuentyl succinicacid in 150 neutral oil, sufficient to supply 1 mole of the acid, wasdissolved in 2 volumes of ethyl ether and volume of concentrated H 50and placed in a reaction flask. An excess of 2 moles of isobutene wasadded and the mixture was shaken for a period of 12 hours under apressure of 50 psi. at 25 C. The mixture was then washed with hot H 0and the excess H neutralized with solid Na CO The mixture was washedrepeatedly with H 0 and then the ether stripped from the mixture and theremaining H O removed as a separate phase. Yield of the ester was 86%based upon amount of acid charged.

Example I V.-Preparati0n of polybatenyl methyl acid saccinate 2 moles ofmethanol were mixed with 1 mole of polyisobutenyl succinic anhydrideprepared according to Example I. The mixture was heated to 60 C. andheld for 2 hours. The excess of methanol was removed under vacuum. Yieldof the half ester was essentially equal to theoretical.

Example V.Preparation of polyz'sobutene di-n-butyl succinate 1 mole ofpolyisobutenyl succinic anhydride and 6 moles of n-butanol were placedin a reaction flask equipped with a thermometer and reflux condenser.The mixture was allowed to reflux for 2 hours. One mole of B 0 was thenremoved by slow distillation of the excess alcohol. The product wasdi-ester and 5% monoester.

The detergent effect of the additives of this invention was demonstratedin the case of spark-ignition engine fuels in a simulated urban-suburbanlaboratory engine test and in actual automobile tests. A diesel enginetest was used to demonstrate effectiveness in diesel type fuel and amodified ASTM-CRC Fuel Coker Test (D-1660) was used to determinesuppression of high temperature deposit formation and filter plugging injet fuels.

The simulated urban-suburban engine test mentioned above is a testdesigned to duplicate the conditions encountered in every daystop-and-start driving. The engine used was a F-956 Chevrolet V-8 of 283cubic inch displacement. The engine was cycled in a pattern under thefollowing running conditions:

Each cycle was repeated eight times, after which the engine was shutdown for 3 minutes, restarted, and the cycles repeated. The completetest was hours.

At the end of the test, the engine was dismantled and the intake valvesand ports were visually inspected for deposits. A rating scale of 0 to10 was used, a rating of 0 indicating a perfectly clean valve or portand 10 indi-. cating very heavy deposits. The deposit from each valvewas also weighed.

The gasoline used in the test was of premium grade and contained 2.06ml. per gallon of tetramethyl lead. The four different base fuels usedare indicated by letter A through D. The polyisobutenyl succinic acidwhich is referred to as PIBSA, and the derivatives thereof listed in thefollowing table contained about 60 carbon atoms in the alkenyl radical.The oil which is referred to in the table was a light petroleum oilhaving a viscosity of 60 SSU at 100 F.

TABLE I.-URBAN-SUBURBAN CYCLE ENGINE TEST DATA Valves Test CompoundConc., Ports,

p.p.m. Rating Rating Deposit None (base fuel) 5.9 3.42 6.0 PIB SA 500-0. 0. 29 0-0. 5 P13 SA 200 0. 4 0.28 0.0 None (ba 5.1 3.15 6.8 PIBSA100 2.9 1.83 3.0 None (base fuel 4. 3 2. 32 5.6 7 1 7, 3.0 2.49 4.6 sPIBSA+Oil 100+7,000 0.9 0.92 0.7 9 None (base fuel) 3.6 1.67 4.0 10Di-tert-butyl ester of 300+7,000 0.4 0.35 0.3

PIBSA+OiL 11 None (base fuel) 6.4 4.03 6.0 12 Di-n-butyl ester of100+7,000 4.3 3.2 4.0

PIBSA+0iL PIB SA: Polyisobutenyl Succinic Acid.

It is apparent from the above data that the additives In the testprocedure adopted, each engine was disof this invention impartsurprising deposit-suppressing assembled and each intake valve and portwas visually characteristics to spark-ignition engine fuels or gasolinesrated for the amount of deposit on a scale from 0 to in which they areemployed. These data show that the 10 with 0 representing a completelyclean port and acids and the esters of this invention each display this10 representing a Very heavy deposit. One valve and favorablecharacteristic and that the addition of a light port were removed andcleaned and the total weight of oil to the composition further enhancesthe detergent or deposit was determined, this figure representing thedispersant effect. It is also evident that the esters derivedequilibrium deposit for the engine. The engine was refrom branched-chainalcohols, such as tertiary butyl alcoassembled and each auto was thendriven for 5000 miles hol are superior to the derivatives ofcorresponding norunder ordinary urban-suburban operating conditions withmal alcohols such as n-butyl alcohol. a fuel composition consisting of agasoline of the same In order to further demonstrate the detergent anddetype previously employed in the auto and 500 ppm. of posit-suppressingcharacteristics of these additives when the additive being tested. Atthe end of the test period they are employed in spark-ignition fuels,fuel composieach engine was disassembled and the valve which had tionscontaining various of these additives and related been removed at thebeginning of the test was visually compounds were evaluated under fieldtest conditions in rated and cleaned, and again removed and the depositprivate automobile engines. In the tests standard Ameriweighed. Thedifference between this weight of deposit can automobiles were employed.At the beginning of the and the previously determined equilibriumdeposit is extest, each auto had been driven a sufiicient length of timepressed in terms of percent of equilibrium deposit in to accumulate anequilibrium deposit in the intake mani- Table II as Deposit Prevention.Negative values indifold and upon the intake valves. The equilibriumposit is the amount of deposit that is normally accumulated afterextended operation with similar fuels. When this amount is deposited, ithas been found that further cate a resulting deposit increase. Theundisturbed valves which had been previously rated by inspection werererated and the difference between the two deposit ratings is expressedin Table II as Deposit Reduction.

TABLE II.--DEPOSIT SUPPRESSION AND REDUCTION IN TEST AUTOMOBILES DepositLevels Percent Deposit Deposits on Reduction Clean Valves PercentDeposit Compound Initial Rating Final Rating Preven- Be'ore A ter tionValves Ports Cleaning Test Valves Ports Valves Ports PolyisobutenylSuccinic Anhydride (derived from Polybutene, average molecular wt.1,000) 5. 9 3. 6 5. 2 2. 3 12 36 3. 2 2.0 40 Polyisobutenyl SuccinicAcid (derived from Polybutene, average molecular wt. 1,000) 2. 7 2. 0 2.6 1. 8 4 10 2. 0 1. 0 Polyisobutenyl Succinic Acid (derived fromPolybutene, average molecular wt. 500) 5. 8 2. 6 5. 4 2. 0 7 23 5. 0 3.0 40 Polyisobutenyl Suceinic Acid (derived from P0lybutane, averagemolecular wt. 3,000) 5. 9 3. 8 4. 4 2. 7 25 29 7. 8 2. 0 MonomethylPolyisobutenyl Succinate (derived from Polybutene, average molecular wt.1,000) 4. 9 3. 1 4. 2 2. 3 14 26 5. 3 2. 0 63 Octadecenyl SuccinicAnhydride 4. 6 3.8 5.4 3. 5 18 8 2.0 6.0 *200 Tetrapropenyl SuccinicAcid 4. 3 3. 2 4. 5 2. 6 *5 18 2. 5 6. 0

* Indicates deposit increase.

operation under normal conditions results in essentially no furtherbuild-up of carbonaceous material. Prior to the test each auto had beenoperated on a high grade The above data show that the additives of thisinvention display extremely good deposit suppressing and reducingproperties under typical driving conditions. It will be noted that thecompounds produced from low molecular weight polyolefins, as shown bythe asterisk marked values, do not give these characteristics, instead,their addition results in a substantial increase of the already existingdeposits and in the formation of new deposits in excess of theequilibrium deposit. Thus, the aforementioned detergent characteristicsof the higher molecular weight derivatives are unexpected.

In order to demonstrate effectiveness of the additives of the presentinvention in reducing the amount of deposits in diesel engines, anengine test was performed using 200 ppm. of polyisobutenyl succinicanhydride in a base diesel fuel and comparing the weight of depositsresulting inside of the fuel injector tips with the deposit from thebase fuel alone. Use of this additive resulted in a substantialreduction in weight of deposit.

In order to determine the utility of these additives in I jet fuels, ajet fuel containing 200 ppm. of polyisobutenyl succinic anhydride wastested in the modified CFR Fuel Coker Test which correlates with theASTM CRC Fuel Coker Test (D-1660) and compared with the base fuelwithout additive. The modified test is run at a fuel passage rate of 2.8lbs. per hour in contrast to 6 lbs. per hour for the standard ASTM test.The temperature of the modified test is 475500 F. as compared to the300-400 F. operation temperature in the standard test. The test showedthat the addition of minor amounts of the above-named compoundeliminated filter plugging and substantially reduced preheater tube andfilter discoloration.

Thus the use of the additives of this invention with spark-ignitionfuels, compression ignition fuels and jet type fuels is specificallycontemplated.

Spark-ignition fuels in which use of the present additives iscontemplated are fuels in the gasoline boiling range, includinghydrocarbon base fuels boiling substantially in the gasoline boilingrange of from about 100 F. to about 450 F. These fuels may be leadedfuels, i.e. fuels containing lead alkyl additives such as tetraethyllead, tetramethyl lead and like compounds which are introduced into thecompositions to prevent preignition and engine knock.

Compression engine fuels or diesel type fuels are hydrocarbon basefuels, for example, distillate fuels cornprising a mixture ofhydrocarbons boiling substantially in the range of from about 300 F. toabout 750 F. and particularly from 350 to 700 F. Such fuels are commonlyderived from crude petroleum oils, from shale oils, from synthetichydrocarbons as example, from the Fischer-Tropsch synthesis, and fromother sources.

Jet fuels.Fuels commonly employed in aircraft jettype and turbineengines are liquid hydrocarbons boiling substantially in the range offrom about F. to about 650 F: The specific fuels vary according to theuse and type of engine. Specific examples of the types of turbine andjet fuels are military grades such as J P4, the specified boiling range.of which is from F. to 550 F. and ]P5 with specified boiling range offrom 326 F. to 550 F. An example of a commercial jet fuel is J P6 whichhas specification boiling limits of from 250 F. to 550 F. An example ofaturbine fuel is commercial turbine fuel which has a boiling rangebetween 260 F. and 406 F.

In addition to the additives of this invention, the use of otherconventional fuel additives is contemplated. Thus the fuel compositionsmay also contain surfaceignition suppressants, such asphosphorus-containing compounds, dyes, gum inhibitors, and oxidationinhibitors.

What is claimed is:

1. A hydrocarbon fuel composition capable of reducing intake valve andport deposits comprising a major proportion of a distillate hydrocarbonmixture boiling substantially in the range of from 100 F. to 750 F. andfrom 50 to 1,000 ppm. of a succinic acid derivative selected from thegroup consisting of (A) an alkenyl succiuic acid,

(B) an alkenyl succinic anhydride, and

(C) an alkenyl succinic ester in which the alkoxy group contains from 1to 6 carbon atoms, wherein the alkenyl groups (A), (B), and (C) containfrom 50 to 250 carbon atoms.

2. The fuel composition of claim 1 in which the succinic acid derivativeis the di-tertiary butyl ester of polyisobutenyl succinic acid.

3. The fuel composition of claim 1 in which the distillate hydrocarbonmixture is a spark-ignition fuel boiling substantially in the range of100 F. to 450 F.

References Cited UNITED STATES PATENTS 2,312,790 3/1943 Backofi' et al.4470 2,922,706 1/1960 Durr et al. 44-70 2,993,772 7/1961 StrOmberg 44702,993,773 7/1961 Stromberg 4470 3,031,278 4/1962 Buckrnann et a1 44-583,172,892 3/1965 LeSeur et al. 252-51.5 3,234,131 2/1966 Morway 252563,255,108 6/1966 Wiese 252-56 FOREIGN PATENTS 981,850 l/ 1965 GreatBritain.

DANIEL E. WYMAN, Primary Examiner.

W. J. SHINE, Assistant Examiner.

1. A HYDROCARBON FUEL COMPOSITION CAPABLE OF REDUCING INTAKE VALUE ANDPORT DEPOSITS COMPRISING A MAJOR PROPORTION OF A DISTILLATE HYDROCARBONMIXTURE BOILING SUBSTANTIALLY IN THE RANGE OF FROM 100*F TO 750*F. ANDFROM 50 TO 1,000 P.P.M. OF A SUCCINIC ACID DERIVATIVE SELECTED FROM THEGROUP CONSISTING OF (A) AN ALKENYL SUCCINIC ACID, (B) AN ALKENYLSUCCINIC ANHYRIDE, AND (C) AN ALKENYL SUCCINIC ESTER IN WHICH THE ALKOXYGROUP CONTAINS FROM 1 TO 6 CARBON ATOMS, WHEREIN THE ALKENYL GROUPS (A),(B), AND (C) CONTAIN FROM 50 TO 250 CARBON ATOMS.